when I try to convert this Hex: 780000465257A7054F5180E46C000100004652 to a decimal number, it should give me this decimal value: 2676089517297180626710225817179225498977322578,

you can try that using this website: Hexadecimal to Decimal

but in PHP I use this code to convert the same hex to decimal:

echo hexdec("780000465257A7054F5180E46C000100004652");

the problem is, it gives me this value: 2.6760895172972E+45

this is not the right value at all.

what is the problem and how to solve it ?